1. Lab 10 Paging

2. NCHU System & Network Lab
Paging
A memory management scheme that permit the physical-address space of a process to be noncontiguous
Physical memory is broken into fixed-sized blocks called frames
Logical memory is also broken into blocks of the same size called pages
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3. NCHU System & Network Lab
Paging
Basic method f
logical
address
physical
address f d
CPU p d f d
target cont. f p f
page table
physical
memory
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4. NCHU System & Network Lab
Basic method
Address format
page number
page offset p d
m-n n m
size of logical address space = 2m
block size = 2n bytes
there are 2m-n pages
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5. NCHU System & Network Lab
Hierarchical Paging
logical address p1 d p2 p1 p2 d
outer-page
table
physical
memory
page of
page table
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6. NCHU System & Network Lab
Hierarchical Paging
Address format
page number
page offset p1 d p2 10 10 12
block size = 4 Kbytes = 212 bytes
page of page table size = 1block size, each entry need 4bytes=>210 entries
210 * 210 * 4 Kbytes = 4 Gbytes (32-bit machine)
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7. NCHU System & Network Lab
fopen
#include <stdio.h>
FILE *fopen(const char *filename, const char *mode);
Mode:
r - open for reading
w - open for writing (file need not exist)
a - open for appending (file need not exist)
r+ - open for reading and writing, start at beginning
w+ - open for reading and writing (overwrite file)
a+ - open for reading and writing (append if file exists)
Return : FILE pointer for success, 0 for error.
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8. NCHU System & Network Lab
Example
One memory states file
2000 addresses ( 0x000 ~ 0x7d0 )
Three frames, 256~511, 768~1023, 1536~1791 have data
Map them to continue logic address 0x000~0x2ff
Basic method paging program
Input one logic address
Output physical address and its data
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9. NCHU System & Network Lab
Example Graph
000
logical address p d
100 1 a b
256
index
1ff
Phy_addr = ab
100 1
300
300 2
600 ab
3ab
content
page table
3ff
600
frame size = 256 bytes = 28
3 frames => logical address : 000 to 2ff
6ff
7d0
physical memory
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10. NCHU System & Network Lab
Example code
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11. NCHU System & Network Lab
Example Result
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12. NCHU System & Network Lab
A program that
use 2 Layer Hierarchical Paging method
one input files (have physical memory states)
frame size = 16 bytes
first layer have 3 entries
second layer need 3 pages, each page has 16 entries
Input logical address
Output physical address and its content
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13. NCHU System & Network Lab
Lab Graph
zoom out
000
000 p1 p2 d a
00a
100 a b
1a0
000
020
040
index
outer page table 1 2
020
1a0
1ff
16 entries
300
040
3ff
04f
page of page tables
600
1a0 b
content
1ab
1af
16 bytes
zoom out
6ff
7d0
Phy_addr=1a0+00b
physical memory
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14. NCHU System & Network Lab
Reference
Advanced Programming in the UNIX Environment 2nd Author : Richard Stevens, Stephen A.Rago, Publisher : Addison-Wesley
Beginning Linux Programming Author : Richard Stones, Neil Matthew Publisher : Wrox
Operating System Concepts 6th edition
Author : Abraham Silberschatz, Peter Baer Galvin, Greg Gagne
Publisher : John Wiley & Sons, inc.
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